Signals from Global Navigation Satellite Systems (GNSS), such as the global positioning system (GPS) system utilized in the United States, are very weak and usually cannot be seen indoors or underground. A common method to overcome the problem of receiving GNSS signals indoors or underground is to use a radio frequency (RF) repeater located outdoors to receive the GNSS signal and re-transmit the signal indoors.
However, there are two limitations to this approach. First, the repeater will only render a position at the receiving antenna point (outside), not at the desired inside point. Second, a low-loss coaxial cable and signal amplification are required to bring the signal from the outdoor point to an indoor space and running this special cable can be prohibitively expensive.